|Publication number||US7133684 B2|
|Application number||US 10/820,534|
|Publication date||Nov 7, 2006|
|Filing date||Apr 8, 2004|
|Priority date||Jun 9, 1999|
|Also published as||US6725047, US7483706, US20040192298, US20070049294, US20090175242, WO2000076137A1|
|Publication number||10820534, 820534, US 7133684 B2, US 7133684B2, US-B2-7133684, US7133684 B2, US7133684B2|
|Inventors||Kevin Farley, Thomas Gorsuch|
|Original Assignee||Ipr Licensing, Inc.|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (14), Non-Patent Citations (6), Referenced by (3), Classifications (26), Legal Events (2)|
|External Links: USPTO, USPTO Assignment, Espacenet|
This application is a continuation of U.S. application Ser. No. 09/328,663, filed Jun. 9, 1999 now U.S. Pat. No. 6,725,047. The entire teachings of the above application(s) are incorporated herein by reference.
The present invention relates to a wireless communication system. In particular, the present invention relates to using a floating address for use in roaming network service.
The present invention provides an addressing protocol for use in a wireless computer network in which a subscriber is assigned a network address based upon an original location in the network. As the subscriber moves throughout the network, data for the subscriber is routed to a cell site server at the subscriber's original location. The cell site server determines whether the subscriber is located in the original cell site, in which case it causes the data to be transmitted to the subscriber over a wireless link, or whether the subscriber has moved to a location serviced by a second cell site server. In the latter case, the first cell site server causes the data to be tunneled to the second cell site server.
To connect to the Internet, every terminal requires an Internet Protocol (IP) address that uniquely identifies the node's point of attachment to the Internet. In other words, a node must be located on the network as indicated by its IP address to receive data destined to it; otherwise, data destined to the node would be undeliverable. IP network address allocation and administration have historically assumed that there is a close relationship between a computer's IP address and its physical location.
In a wireless communication network, however, a subscriber can travel between various cells, thereby receiving transmissions from a variety of base stations. The transmissions are handed off from one base station to another as the subscriber travels from one cell to another. If such a system were to be attempted for Internet routing, when a terminal connects to the Internet while in a particular cell, the base station in that cell connects to a server that provides the IP address for the mobile unit. As the terminal moves through the geography and approaches another base station, a handoff is performed. That is, the transmission between the terminal and the base station is handed off to another base station. This other base station is now responsible for routing data packets.
Of course, moving across a network creates addressing problems that are peculiar to the mobile environment. Specifically, as a terminal moves from point to point on a network, the network must somehow know where the terminal is located so that data packets can be delivered to the terminal. If the terminal requests data in one cell, for example, and travels to another cell, the network must know the terminal's present location so that data packets can be accurately delivered. Unfortunately, because a base station in a first cell may not be in direct communication with a base station in a second cell, traffic can be lost during a handoff. Thus, when a handoff occurs, a terminal's connection to the Internet can get dropped because the new base station does not know the terminal's IP address for data exchange with the Internet.
To account for this addressing problem in the current art, if one connects to the Internet in a mobile environment, a technique called Mobile IP is used. This Mobile IP is a modification to IP that allows nodes to continue to receive data no matter where they happen to be attached to the Internet.
Internet nodes typically use the IP address of a destination node when searching for connections to that destination. Thus, the IP address of a remote endpoint also serves to identify the endpoint. For mobile computers, a destination network is known as the home network. Since the mobile node appears to the rest of the Internet as if it were actually located on the home network, it can be called the home address of the mobile node. If the source of the packet is assumed to be an Internet node with no special modification for mobility support, the source will be unaware whether anything special happens when a packet arrives at the home network.
If, however, the mobile node is not directly attached to its home network, then the packet requires a “care of” address to find the next node. Because the packet can only follow the mobile node by utilizing the existing Internet infrastructure for the intervening hops, Mobile IP changes the data's address scheme so that a packet is able to follow the mobile node off the home network. This operation of changing the address of the packet for further routing is known as readdressing. The operation of readdressing a packet transforms its original destination IP address, the home address that identifies the mobile node, into a different destination IP address, namely, the care-of address, which locates the mobile node.
Additionally, for supporting mobility, the inverse of the readdressing function must be performed. That is, if one agent applies an address translation function to a packet destined for a mobile node, the inverse function should be provided so that the nodes with which it corresponds can operate in a symmetrical manner. Otherwise, the mobile node's home address, identifying the higher-level protocol connection status control blocks, would not be available in the same way as expected by the node that originally sent the packet. Typically, higher-level protocols do operate in this symmetric fashion.
The care-of address is used in lieu of an IP address, but requires a new set of protocols and modifications to the existing network stack.
Because of the need for a care-of address, a central location must be maintained that collects all traffic to be forwarded. Additionally, modifications must be made to network components and the existing network stack. Furthermore, a new set of protocols are required to employ Mobile IP. None of these alternatives are optimal, given the severe scaling problems that are especially relevant considering the explosive growth in mobile computers.
Thus, a need exists in the current state of the art for a mobile network that does not require substantial modifications to the existing network components and protocols.
To alleviate the problems inherent in the prior art, systems and methods are introduced that allow for roaming subscribers to send and receive data on a network in a direct way.
In one embodiment of the present invention, data for a subscriber is received in a first cell. Using a wired-network address in the received data, the intended subscriber is identified, and once the subscriber is identified, it is determined whether the data was received via a tunnel on a backhaul network. If the data was received via the tunnel, then the wireless-network identifier of the subscriber is retrieved, and the data is sent to the subscriber. If the data was not received via a tunnel, it is determined whether the subscriber is presently located in the first cell if the subscriber has traveled to a second cell. If the subscriber is located in the first cell, the wireless-network identifier is retrieved from a database, and using this identifier, the data is transmitted to the subscriber. If the subscriber is not located in the first cell, the cell site in which the subscriber is presently located is identified, and the data is sent via a tunnel to that cell.
The subscriber's wired-network address can be requested from an address server. The address server identifies the originating cell site of the wired-network address, and an unoccupied address that is associated with the originating cell site is assigned to that subscriber. If the wired-network address expires, or is near expiration, a request is received to renegotiate the wired-network address lease. The address server then determines the present location of the subscriber. If the subscriber is not in the same call site as when it received its present address, the present cell site is identified, the request is denied, and a new wired-network address is assigned to the subscriber. This new wired-network address is associated with the cell site in which the subscriber currently resides.
The foregoing and other objects, features and advantages of the invention will be apparent from the following more particular description of preferred embodiments of the invention, as illustrated in the accompanying drawings in which like reference characters refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention.
The present invention relates to a wireless communication system. In particular, the present invention relates to a roaming network service.
The communication system 100 can be adapted to communicate with a computer network 200 such as the Internet. Each cell site server 120 a–120 c is associated with a predetermined number of network addresses that are relevant to data routing functions that can be performed by the computer network 200. For example, in an Internet application, a cell site server 120 a can be associated with a predetermined number of IP addresses. One of the addresses is associated with a “tunnel” function described herein. The other addresses can be associated with subscribers on a dynamic basis. The cell site servers 120 a–120 c can be provided in direct communication with the computer network 200 as shown in
The communication system can include a plurality of mobile stations 140. The mobile stations 140 can communicate selectively with the base stations 130 a–130 c of the communication system 100 over radio frequency communication links using, for example, Code Division Multiple Access (CDMA) transmissions. As the name implies, the mobile stations 140 can migrate 7 throughout the cell sites 110 a–110 c of the communication system 100.
The communication system 100 also can include an address server 150. The address server 150 contains in memory a table of the various network addresses of the cell site servers 120 a–120 c. An example of an address server 150 is a DHCP server. The address server 150 can communicate directly with the computer network 200 as shown in
At step 202, the address server identifies, from its database, an unoccupied address associated with the originating cell site. At step 203, the address server marks the address as in use, and at step 204, the address server 150 transmits the address to the cell-site server, identifying it as being assigned to the subscriber. The cell-site server 120 a then stores information associating this wired-network address with a specific subscriber at step 205.
After the address is assigned to a subscriber, the subscriber can roam the network, being handed off from one base station to another as the subscriber travels from one cell to the next. At an appropriate time in the roaming, the mobile station communicates with a second cell site server. This communication can include telling the second cell-site server the mobile station's wired network address, or a wireless-network identifier such as an electronic serial number (ESN).
If the data was received via a tunnel, then at step 303, the cell site server 120 a retrieves a wireless-network identifier for the intended subscriber, and repackages the data (step 304) for transmission to the subscriber. For example, the wireless-network identifier can be an electronic serial number (ESN). (The invention is not, however, limited to the use of an ESN; any suitable identifier can be used.) At step 305, the cell site server routes the data to the base station for transmission to the subscriber.
If at step 303 the data was not received via a tunnel, then at step 306, the intended subscriber's record is received from a database, and the cell site server determines whether the mobile station is in the cell site of the cell site server 120 a. If the subscriber is presently located in the cell site of cell site server 120 a (i.e., the cell that is serviced by the cell-site server), then at step 303, the subscriber's wireless-network identifier is retrieved, the data is repackaged for transmission by a base station at step 304, and is routed to the base station for transmissions to the subscriber at step 305.
If the subscriber is not presently located in the cell serviced by the cell-site server, then at step 307, using the subscriber's record, the cell site server retrieves a tunnel address of a cell site server 120 b associated with the mobile station. The cell site server 120 a repackages data for the cell site server 120 b and tunnels it using the tunnel address.
It should be understood that
For the purposes of this application, memory includes any medium capable of storing instructions adapted to be executed by a processor. Some examples of such media include, but are not limited to, RAM, ROM, floppy disks, CDROM, magnetic tape, hard drives, optical storage units, and any other device that can store digital information. In one embodiment, the instructions are stored on the medium in a compressed and/or encrypted format. As used herein, the phrase “adapted to be executed by a processor” is meant to encompass instructions stored in a compressed and/or encrypted format, as well as instructions that have to be compiled or installed by an installer before being executed by the processor.
The present invention has been described in terms of several embodiments solely for the purpose of illustration. Persons skilled in the art will recognize from this description that the invention is not limited to the embodiments described, but may be practiced with modifications and alterations limited only by the spirit and scope of the appended claims.
While this invention has been particularly shown and described with references to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the scope of the invention encompassed by the appended claims.
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|U.S. Classification||455/456.1, 455/445, 455/432.3, 455/414.1|
|International Classification||H04W8/26, H04W80/04, H04W36/08, H04L29/06, H04L29/12, H04L12/56|
|Cooperative Classification||H04W80/04, H04L61/2084, H04L29/12216, H04L61/2015, H04L29/12273, H04W36/08, H04L29/12311, H04L61/2053, H04W8/26|
|European Classification||H04L61/20A1, H04L61/20H, H04W80/04, H04L61/20D, H04L29/12A3A, H04L29/12A3H, H04L29/12A3D|
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